Nov’07 DC Power Principles
Nov’07
DC Power Principles
Why DC Power
DC Power System – Overview
DC Output Current flow
Terminology
Provisioning considerations
DC Power System Principles
Types of Power Systems
DC OUTPUT
DC/DC CONVERTER
AC INPUT
POWER SUPPLY OR RECTIFIER
BATTERY CHARGER
Battery
UPS
INVERTER
~ =DC OUTPUTDC INPUT = =
AC OUTPUTDC INPUT = ~DC
OUTPUT
AC INPUT ~ =
AC OUTPUT
Battery
DCAC INPUT ~ = = ~
Provide reliable DC Power for Telecom Equip.No.
1
2
3
4
5
No.
1
2
3
4
5
Battery
DC OUTPUTAC INPUT ~ =
• Most telecom equipment is designed to operate with DC input voltage.
Why choose DC Power ?
Provide equipment power when AC is absentNo.
1
2
3
4
5
No.
1
2
3
4
5
• When the AC supply (mains) is absent, DC supply must come from a stored energy source.
• Currently, DC batteries are the cheapest and most efficient way to store electrical energy.
Battery
DC OUTPUTAC INPUT ~ =
Why choose DC Power ?
Charge the BatteriesNo.
1
2
3
4
5
No.
1
2
3
4
5
• When the AC supply (mains) is restored, the batteries must be recharged.
• Currently, DC batteries can only be charged by DC Power.
Battery
DC OUTPUTAC INPUT ~ =
Why choose DC Power ?
Filter out noise and protect from surgesNo.
1
2
3
4
5
No.
1
2
3
4
5
• A DC supply will act as a line filter thus shielding the telecom equipment from AC system and phase noise.
• A DC supply can also be configured with Over Voltage Protection to prevent high voltage surges from damaging the telecom equipment
Battery
DC OUTPUTAC INPUT ~ =
Why choose DC Power ?
~~~
Monitor and Control the powerNo.
1
2
3
4
5
No.
1
2
3
4
5
Battery
DC OUTPUTAC INPUT ~ =
• Equipment operators can configure and control what power is being supplied to the various telecom equipment.
• Alarming is also provided to monitor the power system’s operation
Why choose DC Power ?
In summary
The reasons for a DC Power System are :
1. Convert AC power to DC for telecom equipment
2. Provide power when AC is absent.
3. Charge the batteries when mains is restored.
4. Provide filtering and surge protection.
5. Provide monitoring and control of power.
DC Power System Principles
Why DC Power
DC Power System – Overview
DC Output Current flow
Terminology
Provisioning considerations
G
DIESELGENERATOR
AC input
Typically AC Mains between 110 – 480V, however other sources of supply can include generators, UPS etc.
AC input
Typically AC Mains between 110 – 480V, however other sources of supply can include generators, UPS etc.
AC Input
DC Power System - Components
G
OVP
MAINS FUSES
DIESELGENERATOR
Input protection
Can be provided by either; in-line fuses, Over Voltage Protection or other such devices.
Input protection
Can be provided by either; in-line fuses, Over Voltage Protection or other such devices.
AC Input
DC Power System - Components
Rectifier#1
Rectifier #2
Rectifier #n
G
OVP
MAINS FUSES
REDUNDANT RECTIFIER
SYSTEMAC/DC
DIESELGENERATOR
Rectifier #n
Rectifier
A Power supply which converts Alternating Current to Direct Current; typical output below 60V.
Rectifier
A Power supply which converts Alternating Current to Direct Current; typical output below 60V.
AC Input
DC Power System - Components
ALARM ALARM MODULEMODULE
Rectifier#1
Rectifier #2
Rectifier #n
G
OVP
MAINS FUSES
REDUNDANT RECTIFIER
SYSTEMAC/DC
DIESELGENERATOR
Rectifier #n
Monitor & Control Unit (Alarm module)
Monitors the system and generates alarms if an event occurs outside of normal operation.
Monitor & Control Unit (Alarm module)
Monitors the system and generates alarms if an event occurs outside of normal operation.
AC Input
DC Power System - Components
ALARM ALARM MODULEMODULE
Rectifier#1
Rectifier #2
Rectifier #n
G
OVP
MAINS FUSES
BATTERY BANK
REDUNDANT RECTIFIER
SYSTEMAC/DC
DIESELGENERATOR
Rectifier #n
BATTERY BANK
Battery Bank / StringA battery bank is 1 or more battery strings.A battery string is a number of batteries connected in series to provide the required operating voltage
Battery Bank / StringA battery bank is 1 or more battery strings.A battery string is a number of batteries connected in series to provide the required operating voltage
AC Input
DC Power System - Components
ALARM ALARM MODULEMODULE
Rectifier#1
Rectifier #2
Rectifier #n
G
OVP
MAINS FUSES
LVBD
BATTERY BANK
REDUNDANT RECTIFIER
SYSTEMAC/DC
DIESELGENERATOR
Rectifier #n
BATTERY BANK
Low Voltage Battery DisconnectTo prevent deep discharging of the batteries.Operated by the MCU when a user-configured low battery voltage point is reached.
Low Voltage Battery DisconnectTo prevent deep discharging of the batteries.Operated by the MCU when a user-configured low battery voltage point is reached.
AC Input
DC Power System - Components
ALARM ALARM MODULEMODULE
Rectifier#1
Rectifier #2
Rectifier #n
G
OVP
MAINS FUSES
LVBD
BATTERY BANK
REDUNDANT RECTIFIER
SYSTEMAC/DC
DIESELGENERATOR
Rectifier #n
LV
LD
BATTERY BANK
Low Voltage Load DisconnectReduces the drain on the batteries by non-priority loads.Operated by the MCU when a user-configured low battery voltage point is reached.
Low Voltage Load DisconnectReduces the drain on the batteries by non-priority loads.Operated by the MCU when a user-configured low battery voltage point is reached.
AC Input
DC Power System - Components
ALARM ALARM MODULEMODULE
Rectifier#1
Rectifier #2
Rectifier #n
G
OVP
MAINS FUSES
BATTERY DISTRIBUTION
BATTERY BANK
REDUNDANT RECTIFIER
SYSTEMAC/DC
DIESELGENERATOR
Rectifier #n
LV
LD
BATTERY BANK
Distribution
System hardware for distributing the DC power to the load. Hardware can include; battery breakers, MCB or blade fuses.
Distribution
System hardware for distributing the DC power to the load. Hardware can include; battery breakers, MCB or blade fuses.
AC Input
DC Power System - Components
LVBD
NONE PRIORITY
LOAD
LOAD(pc’s or different voltage)
ALARM ALARM MODULEMODULE
Rectifier#1
Rectifier #2
Rectifier #n
G
OVP
MAINS FUSES
BATTERY DISTRIBUTION
BATTERY BANK
DC-DC orDC/AC
REDUNDANT RECTIFIER
SYSTEMAC/DC
DIESELGENERATOR
Rectifier #n
LV
LD
PRIORITYLOAD
BATTERY BANK
Load
Any equipment connected to the distribution of the DC system.
Load
Any equipment connected to the distribution of the DC system.
AC Input
DC Power System - Components
LVBD
Load
Any equipment connected to the output of the DC system.
Load
Any equipment connected to the output of the DC system.
NONE PRIORITY
LOAD
LOAD(pc’s or different voltage)
ALARM ALARM MODULEMODULE
Rectifier#1
Rectifier #2
Rectifier #n
G
OVP
MAINS FUSES
LVBD
BATTERY DISTRIBUTION
BATTERY BANK
DC-DC orDC/AC
REDUNDANT RECTIFIER
SYSTEMAC/DC
DIESELGENERATOR
Rectifier #n
LV
LD
PRIORITYLOAD
BATTERY BANK
BATTERY CHARGER
Battery
DC
OUTPUT
AC INPUT ~=
AC Input
DC Power System - Overview
Why DC Power
DC Power System – Overview
DC Output Current flow
Terminology
Provisioning considerations
DC Power System Principles
Eltek Power System
Battery Bank
DC OUTPUTAC INPUT
DC Power System – Current Flow
AC Input OK
AC Input Outage
AC Input restored• Load supplied by DC Power System
• Voltage is at Float Voltage to maintain the charge on the batteries.
Eltek Power System
Battery Bank
DC OUTPUTAC INPUT
DC Power System – Current Flow
AC Input OK
AC Input Outage
AC Input restored• Load supplied by Battery Bank
• Small amount of current to System for alarm and monitoring devices.
Eltek Power System
Battery Bank
DC OUTPUTAC INPUT
DC Power System – Current Flow
AC Input OK
AC Input Outage
AC Input restored• Load supplied by DC Power System
• Batteies recharged by DC Power System. Initially maximum allowable/available current supplied, then reduces as battery charge level increases.
Why DC Power
DC Power System – Overview
DC Output Current flow
Terminology
Provisioning considerations
DC Power System Principles
•W = I x V
•I = W / V
•V = W / I
Terminology – Power Triangle
Current(I)
Power(W)
Voltage(V)
Terminology – Output Characteristics
Constant Power : if the voltage is varied, the current value will
be conversely adjusted to maintain a constant power output.
Constant Current : If the voltage is varied, the power output
will be corresponding adjusted to maintain a constant current
output.
Constant Voltage: If the current is varied, the power output will
be corresponding adjusted to maintain a constant voltage output.
Terminology - Abbreviations
PR : Power Rack; a shelf where rectifiers are inserted.
MCB : Miniature Circuit Breaker
BB : Battery Breaker
MTBF : Mean Time Before Failure; Calculated value of the
probability of failure rates
Why DC Power
DC Power System – Overview
DC Output Current flow
Terminology
Provisioning considerations
DC Power System Principles
NONE PRIORITY
LOADRectifier
#1
Rectifier #2
Rectifier #n
LVBD
BATTERY BANK
Rectifier #n
PRIORITYLOAD
BATTERY BANK
ALARM ALARM MODULEMODULE
MAINS FUSES
BATTERY DISTRIBUTION
LV
LD
3. No. of Outputs ?
AC Input
Provisioning : 6 Key Questions
1. System Voltage ? (+24/-48/-60/other)
NONE PRIORITY
LOAD
PRIORITYLOAD
2. Max Load ?
BATTERY BANK
BATTERY BANK5. Back-up Time ?
Rectifier#1
Rectifier #2
Rectifier #n
Rectifier #n
Rectifier#1
Rectifier #2
Rectifier #n
Rectifier #n
4. Rectifier Recharge time / Redundancy ?
LVBD
6. End Voltage ?
System in normal operation
Provisioning - Redundancy
100A
Battery Charging
Capacity approx 150A, thus “N + 1”
Load
100A
System has no redundancy
Increased recharge time
Provisioning - Redundancy
Load
100A
Can the batteries charge ?
100A
Capacity approx 120A
?
System has no redundancy and reduced standby time
Provisioning - Redundancy
10A
Load
100A
Discharging the batteries
100A
Capacity approx 90A
Provisioning – Battery Breakers
800AhBattery bank
Capacity approx 150A
Load
100A
LVBD
What is the most suitable rating of the BB ?
Too small and it will trip during normal operation; but too big and you waste money
? Charging :150A – 100A = 50 A max
Discharging:100A load max
Thus 150A will suit, though 125A is possible if nec.
Provisioning – Earthing Types
Clean Earth
CABINET
Exchange Link
CABINET
End of Presentation
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